This invention relates to a cooking method and a cooking apparatus capable of saving calorie necessary for cooking, generating desired convection in to-be-heated materials and stirring them during cooking.
When heat-cooking to-be-cooked materials stored in a cooking container, mere heating has been made in the past.
When noodles are boiled, for example, they are heated by boiling water, boiling convection is generated by heating and hot water is fluidized and stirred by this boiling convection so as to loosen the noodles. When such boiling convection (a two-phase stream consisting of hot water and vapor) is generated, latent heat of vaporization must be applied to generate the vapor. Therefore, greater heat energy than really necessary is required. To convert starch to starch paste and to make it easily digestible and absorptible by heating, a boiling temperature of the noodles may sufficiently be around 80.degree. C. (176.degree. F.). In other words, water need not be boiled so as to convert the starch to the starch paste (alpha-starch).
Next, let's take the case, as an example, of cooking of fish soup as a typical example of cooking of soup. It is known that delicious soup can be cooked when heating is gently and slowly made at a relatively low temperature of about 70.degree. C. (158.degree. F.) in the course of a long time. At this time, predetermined convection must be generated inside the cooking container while preventing turbulence in soup inside the container, and stirring must be made lest any turbidity occurs in soup. Such a procedure is directed to prevent ingredients of the soup stock from being disintegrated by boiling and to prevent fine pulverizates from mixing with soup and deteriorating the taste. In this way, soup has high transparency and is visually beautiful. However, it is difficult to generate sufficient convection for stirring soup at such a relatively low temperature of about 70.degree. C. (158.degree. C.). When soup is boiled to obtain strong stirring forcer the taste becomes poor and disintegration of the soup stock occurs due to boiling and soup becomes turbid. As a result, the taste and appearance of soup are deteriorated.
In cooking of stew of meat, on the other hand, it is known that the stew becomes tasty when it is cooked at a temperature of around 65.degree. C. (149.degree. F.). To fully make available the taste of the meat, it is important to make cooking at a temperature near the solidification point of the proteins of the meat, that is, about 65.degree. C. (149.degree. F.). If cooking is made at an excessively high temperature, the meat undergoes shrinkage and becomes harder, and its taste becomes poor. Moreover, the meat becomes difficult to digest. To have the meat impregnated with the broth, however, stirring must be made to a certain extent, and a cook must keep manual stirring at the low temperature described above. In other words, there remains the problem of labor.
When frying tempura and other foods, the temperature for frying is different depending on the materials to be fried. For example, the frying temperature is suitably around 190.degree. C. (374.degree. F.) in the case of a croquette and is around 160.degree. C. (320.degree. F.) for a doughnut, as is well known. To fry the foods at the respective temperatures suitable for them, therefore, the oil temperature must be kept at a predetermined constant temperature. To keep the oil temperature at a temperature suitable for frying, large quantities of cooking materials are divided into small pieces and are then put into the oil, instead of putting them all at one time, to prevent sudden oil temperature full. In the case of tempura and other fried foods, the cooking materials are heated while they float up to the upper layer of the oil. For this reason, the oil temperature at the upper layer portion drastically drops immediately after the cooking materials are put into the oil. However, the temperature of the oil of the lower layer portion near the heat source is kept at a relatively high level. In other words, there is a considerable temperature difference of the oil temperature depending on positions inside the cooking container. To keep constant the oil temperature at the upper layer portion at which the cooking materials float, the oil at the lower layer portion near the heat source is generally heated more than necessary.
The conventional cooking methods, inclusive of the methods described above, all heat merely the cooking container storing therein the cooking materials, and involve the problem that a great energy loss exists for heating because they use calorie more than necessary for cooking. Another problem is that a combination of a temperature suitable for cooking and a desirable stirring stream cannot be obtained by imparting latent heat of vaporization to hot water to generate vapor and effecting agitation by boiling convection of hot water and vapor (a two-phase stream consisting of a mixture of a liquid phase and a gaseous phase). Further, when cocking is made at a relatively low temperature, a cook stirs the cooking materials so as to generate the stirring stream, and the problem of labor remains unsolved.